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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

LUCIA AND ATKEVIDA GLACIERS                              68
vegetation, although there was abundant plant growth above this zone. That part of the glacier which rose above the glacier level on the northern slope of the nunatak was completely covered with a thick coat of moraine by which ablation must necessarily be greatly retarded, so that the thrust which pushed the glacier up may well have occurred years ago, probably long before Russell's visit in 1890. By the advance of 1909 the ice condition around Lucia Nunatak has been greatly changed, as is stated below.
The western margin of the glacier, below Lucia Nunatak, was bordered by a large marginal stream which emerged from an ice tunnel at the southeastern corner of the nunatak and joined the Kwik River, receiving on the way, first a small tributary from the ice tongue west of the nunatak, then land streams from Floral Pass and other valleys in the Floral Hills, and small streams from the glacier. Lucia Stream was an impassable glacial torrent where it emerged from the ice tunnel, but it was swollen to nearly twice that size before it united with the Kwik. Although this stream flowed along the western margin of the glacier it was not everywhere in contact with it, for Lucia Glacier crowds against projecting spurs of the Floral Hills and the stream was at such places forced into rock-walled gorges cut across these spurs. Thus the marginal stream valley consists of stretches where the mountain forms one wall and the glacier the other, alter-nating with short sections enclosed on both sides by steeply-rising rock walls, against whose base the river in places flowed, forcing us, in our attempt to pass up the valley, out of the gorge upon the higher wooded slopes of the projecting spurs.
Conditions on the eastern margin of Lucia Glacier were quite different. Above Terrace Point the snow line was soon reached and the glacier was then in contact with the mountain, but at Terrace Point a broad valley existed, with the moraine-covered ice for one wall and the gravels of Terrace Point for the other wall. In this valley was a small stream, supplied by drainage from the land and from the ice, which, disappeared beneath the ice, but which had earlier in the season been dammed to form a lake. Lacustrine deposits and stream gravels had accumulated here, and the process of formation of the gravels of Terrace Point was here being duplicated and illustrated in miniature. One or two small lakes existed farther down in this marginal valley in the depression between Atrevida and Lucia Glaciers, and below that came the area of coalescence between the crevassed Atrevida and the stagnant Lucia Glacier. Beyond this junction the two lobes flared apart and there was a valley, broadening rapidly westward to a V-shape, in which a small stream flowed over an alluvial fan, bordered on the west side by the low, wooded embankment of Lucia Glacier and on the east side by the similar slope of Atrevida Glacier. This stream evidently carried the drainage from the Terrace Point region plus such water as escaped from the eastern margin of the moraine-covered Lucia and the western margin of Atrevida Glacier. A large part of this water had passed beneath the stagnant interlobate area between the two glaciers. Evidently, therefore, the main drainage of Lucia Glacier was on the west and of the Atrevida on the east side, and the interlobe drainage was moderate in amount. This condition was greatly changed in 1909.
Lucia Glacier has at some former time been far more extensive than now. This is proved by the morainic deposits that cover Terrace Point, and by the moraine terraces that lie high up in Floral Pass and in other valleys in the eastern slopes of the Floral Hills. It has at some period been tributary to the Malaspina, and, while there is no proof of it, it is entirely possible that ice may even at present lie beneath the gravels of